Air release device on air knives



Nov. 5, 1968 J. F. KOSALEK AIR RELEASE DEVICE ON AIR KNIVES Filed May 26, 1967 INVENTOR.

Joseph F. Kosulek ATTORNEY United States Patent 3,408,983 AIR RELEASE DEVICE ON AIR KNIVES Joseph F. Kosalek, Binghamton, N.Y., assignor to GAF Corporation, a corporation of Delaware Filed May 26, 1967, Ser. No. 641,838 2 Claims. (Cl. 11863) ABSTRACT OF THE DISCLOSURE This invention relates to improvements in air knives for paper coating machines. In particular, it refers to an the air knife manifold is provided by attaching an air inair against the surface of a wet coated paper web in order to smooth the coating thereon. Laminar air flow through air knife manifold construction which projects a stream of let conduit at one end thereof, and an air release valve for venting a portion of the air at the other end of the manifold.

This invention relates to improvements in paper coating machines and, more particularly, to an air knife device for evenly and smoothly distributing the coating material over a paper web surface in an improved efficient manner.

In the manufacture of coated or sensitized material, such as for example, diazo-type paper or photographic film, machines are used to apply a liquid coating solution to a web of material to be coated. Generally, the web is dipped into or sprayed with the coating solution or material. Subsequently, the wet coated web of paper is moved in an upward direction, thus allowing excess coating solution to drip down into a run-off trough. Since the spraying of the liquid coating solution onto the paper web resulted in a highly uneven and therefore unsatisfactory distribution of the coating over the surface of the web, air doctor or air knife devices were developed to overcome this particular problem.

Essentially, the air knife devices developed in the prior art, and currently being used in the paper coating industry, constitute hollow elongated manifold members which extend across the width of the coated web and are placed in closely spaced relationship thereto. The air manifolds usually include elongated air jet openings or converging nozzles facing in the direction of the wet coated paper web. Suitable air supply conduits, attached to each end of the manifolds, are adapted to supply air to the interior thereof. The air is then expelled through the air jet openings or nozzles against the surface of the coated web and acts as a doctor blade or knife to evenly distribute the liquid coating solution over the paper web surface.

Although the aforedescribed air doctor blades or air knife constructions have proven themselves to be satisfactory when applied to paper coating machines under certain operating conditions, difficulties have been encountered when operating the air knives at relatively low pressures in connection with the laying down or application of fairly high deposits of various pigmented and nonpigmented aqueous and solvent solutions or emulsions. In effect, the pressurized air converging within the air manifolds from both ends thereof, creates a turbulent air condition which results in an uneven air distribution across the air jet opening or nozzles. This frequently resulted in the coating having incorporated therein irregularly shaped bar marks, zig-zag or herring bone patterns, or dry streaks. These coating defects were completely unacceptable in critical sensitized paper and film base operations, where the even distribution and smoothness of the coated surface layers were of prime importance.

In order to alleviate these shortcomings, apparently caused by the air turbulence within the air knife manifolds and resulting from the introduction of air at both ends thereof, it was decided to close off one end of the manifold. The resultant uni-direction flow of air into the air knife manifolds, it was anticipated, would eliminate the turbulence and consequent uneven air distribution across the air jet openings or nozzles. In practice, however, it became obvious that by closing off one end of the air manifold, the region of air turbulence was not eliminated, but merely relocated or shifted within the air manifold. Consequently, the problem of providing an evenly distributed and smooth coating surface on the paper,'remained unsolved. As a result, these coating defects, so frequently encountered in the sensitized paper and photographic film base coating technology, led to excessive product waste and resulted in rejections by commonly applied standard quality control inspections.

The air knife construction, according to the present invention, overcomes the foregoing and other disadvantages and problems encountered in the prior art by providing a novel and unique air release or valve device at one end of the manifold, which will assure the laminar unidirectional flow of air therethrough. The resultant elfect will be an even flow of air across the width of the wet coated paper web, which emanates from the air jet opening or nozzles of the air knife manifold.

Accordingly, it is a primary object of the present invention to provide an improved air knife device adapted to facilitate the smooth, even coating of a paper web.

Another object of the present invention is to provide a novel air knife device as described herein and which incorporates air release means at one end thereof so as to assure laminar, unidirectional flow of air through the air knife.

A more specific object of the present invention'is to provide an air knife device assisting in the smooth coating of a paper web, and which includes an air manifold having an air inlet source at one end thereof and an air release damping valve at its other end so as to assure laminar, unidirectional flow of air through the air knife device.

These and other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which:

FIG. 1 is a vertical section of an air knife device according to the present invention; and

FIG. 2 is a section view taken along line Z2 in FIG. 1.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, the air knife device 1 includes a manifold member 2. Manifold member 2 is of a substantially cylindrical or tubular cross-sectional configuration and may be formed or cast of a suitable metallic material, such as cast bronze or the like. A preferable construction for manifold member 2 would be mating upper and lower halves 3 and 4 which are adapted to form the closed cylindrical configuration. Mating edge 5 between manifold halves 3 and 4 is shaped to form a converging V-shaped air nozzle orifice 6 extending along the full length of manifold member 2. Each end of manifold halves 3 and 4 extends into a substantially semicircular radially extending flange portion 7, which when assembled into mating relationship, will form a complete circular flange with a complementary flange portion 7.

Suitable bolt holes 8 may be provided in each of the flange portions 7 so as to facilitate assembly with other machine elements. At one end of manifold member 2, a suitable air inlet conduit 9 having a flange 10 is attached to the manifold member. Attachment between manifold I member 2 and conduit 9 is accomplished by suitable threaded fasteners 11 extending through bolt holes 8 in flanges 7 and through aligned bolt holes 12 in conduit flange 10. A sealing gasket 13 may be interposed between flanges 7 and flange to thereby provide a substantially air-tight connection.

At the other end of manifold member 2 an air release damper valve 14 may be attached thereto through the use of suitable threaded fasteners 11 passing through the bolt holes 8 in flanges 7, and through a flange 15 formed integrally with damper valve 14. A sealing gasket 13 may be positioned between flanges 7 and flange 15 to provide an air-tight connection between manifold member 2 and damper valve 14.

The air knife device 1 extends generally horizontally in closely spaced relationship with a backing roll 16 about which a moving web of paper 17 is entrained. Suitable coating solution applicator or spray means (not shown) apply the coating solution onto the surface of paper web 17 before it reaches backing roll 16. As the wet coated paper web 17 passes the orifice 6 of manifold member 2, a stream of air, which is forced into the interior of manifold member 2 from air inlet conduit 9, impinges onto the surface of paper web 17. As a result, the coating on the paper web surface will be evenly and smoothly doctored or distributed under the influence of the air stream.

In order to assure that the air forced into manifold member 2 from conduit 9 flows in a laminar unidirectional manner, a proportionate volume of the air is vented to atmosphere through damper valve 14, while the remainder of the air moves through nozzle orifice 6 against the surface of coated paper web 17. The venting of a portion of the air through damper valve 14 will prevent back-up of air within manifold member 2 and thereby avoid turbulence in the interior thereof. Since the venting of air through damper valve 14 may tend to drop the in tensity of the air stream emanating from nozzle orifice 6 below a required degree, the pressure of the inlet air from conduit 9 may be increased by a proportionate compensating degree.

From the foregoing, it becomes readily apparent that the elimination of air turbulence within manifold member 2 will prevent turbulence and uneven air distribution coating machines in which the present air knife device is across the width of air nozzle orifice 6, thus assuring an even stream of air against the surface of coated paper web 17. This will, in essence, greatly increase the operatinstalled.

Another aspect of the present air knife device 1 dies in that it may be installed in existing paper coating machines in a simple and inexpensive manner, requiring a minimum of mechanical manipulation or replacement of existing machine components.

It should also be understood that the foregoing relates to only a preferred embodiment of the invention, and that it is intended to cover all changes and modifications 0f the example of the invention herein chosen for the pur poses of the disclosure, which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

1. In a paper coating machine including means for applying a coating solution to a web of paper, the combination comprising:

a rotatably mounted horizontal backing roll about which said coated web is entrained,

an air knife means comprising an elongated manifold having an air jet opening extending substantially parallel to said backing roll adapted to direct a stream of air against said coated web across the width thereof,

air inlet means fastened to one end of said air knife means so as to direct air to the interior thereof,

and air release means fastened to the opposite end of said air knife means adapted to continuously vent at least a portion of the air passing therethrough.

2. A machine as defined in claim 1 wherein said manifold includes flange portions at each end.

said air inlet means includes a conduit fastened to one of said flanges,

and said air release means comprises a valve device attached to said other flange.

References Cited UNITED STATES PATENTS 2,733,653 2/1956 Mullen 11863 XR 3,038,441 6/1962 Wamsley 11863 3,196,038 7/1965 Schoch et al 118--63 XR CHARLES A. WILLMUTH, Primary Examiner.

ROBERT I. SMITH, Assistant Examiner. 

